End User's Perspective
From a user's point of view, the advantage of having a distributed time service is that more applications work as expected in a distributed environment. For example, the UNIX make program compiles new binary files if it discovers that the source file has been changed since the last time the binary was compiled. In a distributed system, this may not work properly if the source is on one machine and the binary is on another, and the two machines have different ideas of what time it is (and of what time it was when their files were updated). Having DTS means that the nodes have roughly the same notion of time, and the make program works as expected.